It's good that you are using something other than a wooden prop. Spray from the water will destroy a wooden one quite easily. Maybe a 12 - 5 would be a good prop to try. It will give you a little more clearance between the water and the prop tips. You might also try putting a piece of yarn on your antenna (assuming it isn't a 2.4 GHz one - too short) and using that to determine wind direction. That way you wouldn't have to wait to let the plane weather vane.